Applicant""s invention relates to the joining together of two pieces of material by welding.
Welding is a well-known and widely-used method used to permanently join together two pieces of metal tubing or other weldable material. To accomplish a weld of high integrity, the two pieces to be joined together must be properly aligned.
Misalignment during welding creates discontinuities at the abutment junction of the two pieces of weldable material that can serve as havens for particle impurities. The existence of these particle xe2x80x9csitesxe2x80x9d is intolerable when the welding is being performed in connection with ultra-pure applications such as are common in the semiconductor industry. Moreover, misalignment can result in a leaky junction that destroys the purity of the substance flowing through the tubing and creates a potentially dangerous external environment if the substance flowing through the tubing is toxic. Thus, it is highly desirable to minimize tube misalignment when welding.
Maintaining proper alignment during the conventional welding process, however, is a time-consuming and difficult task. The pieces of weldable material to be aligned and welded must be clamped tightly in alignment before and during the welding process, or the pieces will tend to slip out of alignment before the weld is completed.
Conventional orbital weld heads do not solve this slippage problem. In an orbital welding machine, a computer-controlled welding machine works in conjunction with a weld head that also holds the two pieces of weldable material together during the welding process. The weld head is essentially comprised of a system of gears and an electrode for making the weld. The gears control the movement of the electrode as it xe2x80x9corbitsxe2x80x9d around the circumference of the junction between the two pieces of weldable material. Orbital welding is in great demand, especially for welding of tubing of small circumference, because of the ease in which the welding process can be controlled. Orbital welding however, does not solve the problem of misalignment.
To the contrary, the conventional weld head on a standard orbital welder has such little clamping surface area that proper alignment of the pieces of weldable material is often the most significant and time-consuming challenge facing the technician operating the welder. For example, welding is often performed on pieces of weldable material that are many feet in length and that may have hardware or other accessories permanently attached thereto. Because the weld head in conventional welding is typically affixed to a table or bench, the technician is sometimes required to place one end of a weldable material piece upon support blocks so that the weight of the weldable material and any attached hardware does not drag the weldable material out of alignment.
In addition, because of the construction of the conventional orbital weld head, the technician has an extremely limited view of the junction to be welded as he attempts to align the two pieces of weldable material to each other and position the junction of the two pieces in line with the electrode. To aid in the alignment procedure, the technician may use a xe2x80x9cfeelerxe2x80x9d gauge such as a small screwdriver. The feeler gauge is moved by the technician over the top or side of the abutment junction, allowing the technician to determine which of the two pieces of weldable material needs to be moved to improve the alignment. Even after achieving acceptable alignment of the pieces to be welded together, the technician is also required to position the tube junction to be welded in line with the electrode, to ensure a proper weld. The manual performance of these tasks is far from ideal for applications requiring strict alignment and is very time-consuming.
Even if the technician is able to obtain satisfactory alignment at the start of the conventional orbital welding process, the weldable material pieces will tend to separate during the welding process, because hot spots created by the rotating electrode expand to different degrees, thereby creating a twisting effect as the electrode continues its rotation around the abutment junction. An attempt to excessively tighten the clamps on the weld head to overcome this problem usually results in the formation of clamping marks in the weldable material and may result in actual tube deformation.
In an attempt to solve the problem of alignment and the xe2x80x9ctwisting effectxe2x80x9d described above, skilled welders commonly align the two pieces of weldable material and make several temporary spot welds or xe2x80x9ctackxe2x80x9d welds around the circumference of the abatement junction prior to final welding. Tack welds join the two pieces of weldable material together and are sufficiently strong to prevent the separation and twisting effect described above. During final welding, the tack welds merely are re-melted into the final weld.
Even when using tack welding, proper alignment is critical, and therefore, tack welding, by itself, does not address the problem of creating acceptable alignment in a time efficient manner. Although tack welding effectively joins two pieces together prior to performing an orbital weld and makes the orbital welding process much simpler, throughput or productivity, measured in welds per hour, is still limited by the amount of time it takes to align the pieces in preparation for the tack weld.
Applicant""s prior invention, which is the subject of patent application Ser. No. 08/318,385, now U.S. Pat. No. 5,679,271 has addressed this alignment problem by teaching the use of a device which allows two pieces of weldable material to be precisely aligned and tack welded together. Although Applicant""s prior invention is a definite improvement over the prior art, it still is not an ideal solution, because once the tack weld is completed, the technician must then spend time switching instruments to perform a full weld with a conventional orbital weld head.
The present invention expands and improves upon the concept taught by Applicant""s prior invention, by teaching the use of a device that causes two pieces of weldable material to be precisely aligned and completely welded together, thereby eliminating the steps of tack welding and then switching instruments to perform a complete weld.
Thus, the present invention, by mechanizing the aligning task, has all of the benefits of a conventional orbital welder, but greatly reduces the time required to achieve tolerable alignment and eliminates the separation, twisting, and clamp mark problems associated with the use of a conventional orbital welder.
It is an objective of this invention to provide a device and method of operation for said device for aligning and welding together two pieces of weldable material.